The Event Tickets and Registration WordPress plugin before 5.28.4 does not properly escape event titles before outputting them in a ticket history log, allowing users with the Editor role and above to perform Stored Cross-Site Scripting attacks that execute against higher-privileged users on multisite installations.
https://wpscan.com/vulnerability/678a362f-b71d-4308-8fc3-f3bf3e6c3ca9/